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{\Large \bf Abstract}
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Ultrasound is an attractive imaging modality for interventional procedures because it is non-invasive, inexpensive and provides a possibility for real-time acquisition. It is one of the methods of choice for surgeons to monitor interventional procedures such as biopsies or punctures. Accurately tracking the surgical tool is crucial in these procedures since it can increase surgical accuracy and thus reduce the recovery time for the patients. Most of the methods currently employed use modified needles and additional tracking devices to ease the localization of the tool. Although image-based solutions have been proposed, they often remain computationally expensive for real-time applications such as intra-operative robotic imaging. This thesis presents the use of a Hough transform based detector combined with a particle filter to tackle the problem of localizing a flexible needle in real-time. The performance of the method is illustrated with experiments on agar phantoms. This conclusively demonstrates this method's superiority over other image-based methods.\\

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\textbf{Keywords:} needle tracking, ultrasound, particle filter, Hough transform\par
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